This invention relates to data recording equipment, and more particularly to a system adapted for a series of measurements, such as sonar depth sounding, wherein a fixed number of output samples of data is provided for an input data interval of varying duration.
A typical situation wherein data is to be accumulated during an interval of varying duration is that of the sonar sounding situation wherein the data input interval is the length of time in which a sonar signal travels from a transmitting transducer to a reflecting surface, such as the ocean bottom, and returns to a receiving transducer. Typically, such a sonar system is carried by a ship sailing through water of varying depth with the result that the data to be accumulated occurs during an interval of time which varies in accordance with the depth of the ocean. On the other hand, the data output of a sonar system is typically portrayed on a recorder having a recording medium of fixed dimensions upon which the data is displayed.
A problem arises in that such recorders typically utilize a stylus for imprinting marks on the recording medium, the marks representing points of reflection of sonar signals in the ocean. If the stylus transport mechanism is set for a specific speed of stylus movement across the recording medium, then, as the depth increases, there may be insufficient space on the recording medium to imprint all the marks while, as the depth decreases, an increasingly large portion of the recording medium is not utilized at all for the imprinting of marks. One solution to this problem has been the use of selectible gear ratios in a geared transmission of the stylus transport. However, such gearing tends to introduce noise which is particularly dangerous in an environment wherein enemy submarines may be listening for such noise. Also, complex geared transmissions are more prone to wear than a similar stylus transport having but one speed.